arrowhead scaleUnaspis yanonensis Kuwana

Overview

Arrowhead scale is considered native to China but has invaded and
spread though much of Japan, France, and Italy. It is not known to
occur in the U.S. Infested live plants or fruit provide the main method
of introduction to other localities. Hosts include all citrus, especially
oranges, but also a wide range of other crops, including bananas,
coconuts, guavas, hibiscus, jackfruits, kumquats, and pineapples. The
eggs of the first generation are laid under the armor of the adult
female. The orange-yellow egg is entirely smooth and oval. In citrus-producing
areas of the United States, egg laying will most likely begin
in February or March with each female producing about 200 eggs. The
first larval stage (crawler) is an active, flat, oval-shaped, pale-yellow
creature with purple eyes. After the first molt the legs are lost and the
antennae are reduced to a single segment. The body of the adult
female does not change much from this form. Male nymphs have a
pre-pupal stage leading to a winged adult. The prepupa is orange-yellow
with dark purple-brown eyes. The rudimentary antennae, legs,
and wings are visible. The winged male is orange-yellow with deep
dark brownish-purple eyes and is 1/16 of an inch long. A light
brown band can be seen across the thorax. The abdomen narrows at
the end and has a sharp style. Female scale covers are mussel-shell
shaped 1/8 of an inch, slightly convex, blackish-brown with a paler
margin. The scale cover of the male is smaller than that of the female,
white, and elongate oval in shape. There are 2 to 4 generations per year
and development is strongly influenced by air temperatures. Feeding
of the insect produces chlorotic-necrotic spots, irregular growth, and
limb die-back, as well as malformation of fruit and premature drop.